Figure 4: Effect of CatE and peptide aptamers, (a) P3 and (b) S3, on HeLa cells. HeLa cells in 96-well plates were incubated overnight with, cathepsin E and peptide (P3 or S3) mixture at three different molar concentration ratios (cathepsin E : peptide = 1 : 10; 1 : 100; 1 : 1000). After 20 hours of incubation at 37°C, cells were assayed for viability using a Cell Counting Kit-8 (measuring the absorbance at 450 nm) and Cell Counting Kit-F (CCK-F) measuring the fluorescence at 535 nm (excitation at 485 nm) using a microplate reader. Error bars represent average and standard deviation values of three independent experiments. *, **, and *** compared with the control group (only CatE-treated cells) by Student’s -test.